Transgenic and gene targeting technologies will be used in this program project to generate mice strains in which the functions of several genes key to skeletal development and growth are disrupted. Ultrastructural analysis of skeletal tissues from these mice and their wild type littermates will be performed to help characterize these disturbances and delineate the normal functions of the gene products involved. The analyze will focus on the ultrastructure of epiphyseal cartilage, growth plate and bone cells and the structure and organization of matrices assembled in these locations. Established protocols will be employed. The electron microscopy (EM) core in Portland will carry out transmission EM and, when appropriate, scanning EM and immuno(gold) EM studies on the murine skeletal tissues and rotary shadowing of fibrillar constituents of the skeletal matrices. In some instances, i.e., transmission EM, mouse skeletal tissues will be fixed in Houston and shipped to Portland. In other, i.e., immuno EM, mice will be transferred to Portland so that the tissues of interest can be exposed to antibody before fixation. All of these protocols are currently in operation in the facility, and a wide range of antibodies that recognize murine skeletal protein epitopes are available. The investigators, Dr. William Horton and Doug Keene, have a long standing interest and special expertise in this field, and the EM facility in Portland is particularly suited for the proposed studies. Moreover, both investigators have collaborated closely and productively with other PIs in the program project demonstrating how mice, mouse embryos, murine skeletal tissues and information can be easily transferred from one location to the other as well as the effectiveness of this working arrangement. The ultrastructural analyzes to be provided by this core are essential to the overall performance on the program project.